System, method and apparatus for pattern clean-up during fabrication of patterned media using forced assembly of molecules

ABSTRACT

A pattern clean-up for fabrication of patterned media using a forced assembly of molecules is disclosed. E-beam lithography is initially used to write the initial patterned bit media structures, which have size and positioning errors. Nano-sized protein molecules are then forced to assemble of on top of the bits. The protein molecules have a very uniform size distribution and assemble into a lattice structure above the e-beam patterned areas. The protein molecules reduce the size and position errors in e-beam patterned structures. This process cleans the signal from the e-beam lithography and lowers the noise in the magnetic reading and writing. This process may be used to fabricate patterned bit media directly on hard disk, or to create a nano-imprint master for mass production of patterned bit media disks.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.11/946,423, filed Nov. 28, 2007, and is incorporated herein by referencein its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to fabricating patterned mediaand, in particular, to an improved system, method, and apparatus forpattern clean-up during fabrication of patterned media using forcedassembly of molecules.

2. Description of the Related Art

E-beam lithography can be used to form patterned bit media structuresfor hard disk drives. However, when the features being exposed by thee-beam lithography system approach the resolution of the lithographytool, typically there will be unacceptable variations in the size andpositioning of the patterns created. These variations cause problems,such as noise, for magnetically reading and writing on patterned bitmedia structures.

For example, one ideal shape for a “lift-off” e-beam pattern is depictedin FIG. 1. In this process the resolution of the lithography tool issufficient to form uniform dots 11 in a symmetrical array as shown.However, as illustrated in FIG. 2, features that are smaller than theresolution limit of the lithography tool form irregular shapes 21 thatare non-symmetrically arrayed. Although these methods are workable forsome applications, an improved solution for a system, method andapparatus for pattern clean-up during fabrication of even smallerpatterned media would be desirable.

SUMMARY OF THE INVENTION

Embodiments of a system, method, and apparatus for pattern clean-up forfabrication of patterned media using a forced assembly of nano-sizedparticles is disclosed. The invention uses lithography to write theinitial patterned bit media structures, which have size and positioningerrors, and then forces the assembly of the nano-sized particles on topof these bits.

The nano-particles, such as protein molecules, have a very uniform sizedistribution and assemble into a lattice structure above the patternedareas. The protein molecules can be used to reduce the size and positionerrors in patterned structures. This process will “clean-up” the “dirty”signal from the lithography and, therefore, lower the noise in themagnetic reading and writing. This process may be used to fabricatepatterned bit media directly on hard disk, or to make a nano-imprintmaster for mass production of patterned bit media disks.

In one embodiment, a pattern is first fabricated on a disk or imprintmaster using e-beam lithography and a “lift-off” metallization process.First, a positive e-beam resist is exposed and developed leaving smallholes in the resist. A directional metallization process is then used tocoat the sample with a noble metal. Finally, a solvent is used to“lift-off” the e-beam resist and leave behind the noble metal dots.Ideally, this process results in metal dots that are perfectly shapedand positioned. However, when the e-beam lithography tool used tofabricate the features is at or beyond the limits of its resolution,there is some error in shape and position of the dots. The imperfectionscan come from the e-beam dose, positioning errors, problems with the“lift-off” process, etc.

The nano-particles utilized by the invention can have size and shapedistributions that are much more consistent than the spot sizedistributions created with e-beam lithography. The substrate patternedwith e-beam lithography may be placed into a wet solution suspending thebiological agent of choice. For example, the substrate may be placedinto a solution containing chaperonin. At this stage, the chaperoninmolecules bond to the gold dots on the substrate surface. In particular,the thiol group on the cystein protein near the opening of thechaperonin protein interacts with the gold to form a semi-covalent bondthat is about half of the carbon-carbon bond strength.

The foregoing and other objects and advantages of the present inventionwill be apparent to those skilled in the art, in view of the followingdetailed description of the present invention, taken in conjunction withthe appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and advantages of the presentinvention, which will become apparent, are attained and can beunderstood in more detail, more particular description of the inventionbriefly summarized above may be had by reference to the embodimentsthereof that are illustrated in the appended drawings which form a partof this specification. It is to be noted, however, that the drawingsillustrate only some embodiments of the invention and therefore are notto be considered limiting of its scope as the invention may admit toother equally effective embodiments.

FIG. 1 depicts a conventional e-beam pattern having features that arewithin the resolution limits of a lithography tool;

FIG. 2 depicts an e-beam pattern having features that are smaller thanthe resolution limits of a lithography tool;

FIGS. 3A-G are schematic sectional side views of one embodiment of amethod in accordance with the invention; and

FIG. 4 is a schematic top view of the step illustrated in FIG. 3D and isconstructed in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 3 and 4, embodiments of a system, method andapparatus for fabricating patterned media are disclosed. The inventionis well suited for pattern clean-up during fabrication of patternedmedia using a forced assembly of nano-sized particles. Advantageously,the patterned media may be used to directly form disks for disk drives,or form nano-imprint masters for mass production of patterned bit mediadisks.

As shown in FIG. 3A, a substrate 31 is provided with resist 33, such asan e-beam resist, optical resist or block co-polymers. The resist 33 isexposed and developed on the substrate 31 (see FIG. 3B) such that holesor other configurations are formed in the resist. A material 35 such asa metal (e.g., a noble metal like gold) is deposited on the developedthe e-beam resist (see 35 a) and on the substrate (see 35 b) as shown.The noble metal may be directionally evaporated on the developed e-beamresist and substrate to form a coating thereon.

Referring now to FIG. 3C, the e-beam resist 33 and the noble metal 35 aon the e-beam resist are removed from the substrate 31 such that noblemetal features 35 b remain on the substrate 31. This step may comprise alift off metallization process using hot solvent to strip the e-beamresist and noble metal on the e-beam resist from the substrate such thatnoble metal features remain on the substrate. The features may be at orbeyond a resolution of a lithography tool (e.g., e-beam) used to formthe features such that the features have irregular shapes and are notsymmetrically arrayed.

As shown in FIGS. 3D and 4, the invention further comprises attachingnano-sized particles such as molecules 37 to the noble metal features 35b. The molecules may comprise biological agents, such as proteinmolecules, or man-made particles that have a uniform size distribution.The molecules assemble into a lattice structure above the noble metalfeatures such that the protein molecules reduce size and position errorsin the patterned media that will ultimately be formed. In otherembodiments, the molecules may be ultrasonically agitated and/or enzymesmay be used to promote bonding to facilitate self-assembly onto thenoble metal features.

In one embodiment, the molecules comprise chaperonin molecules thatattach to each of the noble metal features. The protein moleculechaperonin is cylindrically shaped with a diameter of about 17 nm.Chaperonin may be created with a thiol functional group connected to it,which readily bonds to noble metals such as gold.

As shown in FIG. 3E, the substrate may be reactive ion etched (RIE) withfluorine plasma to facilitate self-assembly and an orderly, symmetricalarray (see, e.g., FIG. 4) of the molecules onto the noble metalfeatures. In other embodiments, the molecules may be ultrasonicallyagitated and/or enzymes may be used to promote bonding to facilitateself-assembly onto the noble metal features.

In another embodiment, the molecules are magnetic biological agents, andmagnetic fields are used to facilitate self-assembly onto the noblemetal features. In still another embodiment, a monolayer of alkanethiolsis used to facilitate self-assembly of the molecules onto the noblemetal features. The monolayer of alkanethiols may comprise a dithiols(e.g., Sigma-Aldrich 662615) having a thiol function head that formsdisulfur bonds with a thiol group on a cystein protein near an openingof the chaperonin.

After the guided assembly of chaperonin molecules on to the surface ofthe substrate, other processes, such as dry etching can be used totransfer this highly organized and uniform pattern into the substrate.During the etching process the nano-particles act as a mask and protectthe original substrate surface. The etching could be done with processessuch as reactive ion etch (RIE), wet chemical etch, or ion beam etch.The etch process forms a topography on the substrate surface. Forexample, referring to FIGS. 3E and 3F, the method may further compriseremoving the molecules 37 and the noble metal features 35 b from thesubstrate 31 to form a topographically patterned substrate 39. This stepmay be performed with wet etching to form the patterned substrate andsuspend the molecules. Finally, a magnetic media layer 41 is deposited(see FIG. 3G) on the patterned substrate 39 to form patterned media.

The invention has significant advantages over the prior art, includingthe ability to clean dirty signals from e-beam lithography and lowernoise in magnetic reading and writing. The size and positioning errorsformed when using e-beam lithography at its limit of resolution areovercome by forcing an assembly of nano-sized molecules to array on topof the formed bits. The process is quite versatile as it may be used tofabricate hard disks or to create nano-imprinted masters used in theproduction of hard disks.

While the invention has been shown or described in only some of itsforms, it should be apparent to those skilled in the art that it is notso limited, but is susceptible to various changes without departing fromthe scope of the invention.

1. A method of forming a pattern, comprising: (a) providing a substratewith resist; (b) exposing and developing the resist on the substrate;(c) depositing a metal on the developed resist and substrate; (d)removing the resist and metal on the resist from the substrate such thatmetal features remain on the substrate; (e) attaching nano-sizedparticles to the metal features; (f) using the nano-sized particles as amask to protect selected portions of the substrate while exposedportions of the substrate are etched; and (g) removing the nano-sizedparticles and the metal features from the etched substrate to form atopographically patterned substrate.
 2. A method according to claim 1,wherein step (b) comprises forming holes in the resist, and step (c)comprises directionally evaporating the metal on the developed resistand substrate to form a coating thereon.
 3. A method according to claim1, wherein step (d) comprises a lift off metallization process to stripthe resist and metal on the resist from the substrate such that themetal features remain on the substrate.
 4. A method according to claim1, wherein the metal features are at or beyond a resolution of alithography tool used to form the metal features such that the metalfeatures have irregular shapes and are not symmetrically arrayed.
 5. Amethod according to claim 1, wherein the nano-sized particles areprotein molecules that assemble into a lattice structure above the metalfeatures in step (e), such that the protein molecules reduce size andposition errors in the patterned media.
 6. A method according to claim1, wherein step (e) comprises attaching a chaperonin molecule to each ofthe metal features, and step (f) comprises reactive ion etching (RIE)the substrate.
 7. A method according to claim 1, further comprisingremoving the nano-sized particles and the metal features from thesubstrate to form the topographically patterned substrate.
 8. A methodaccording to claim 1, wherein step (e) further comprises agitating thenano-sized particles to facilitate self-assembly onto the metalfeatures.
 9. A method according to claim 1, wherein step (e) furthercomprises bonding the nano-sized particles to the metal features.
 10. Amethod according to claim 1, wherein the nano-sized particles aremagnetic biological agents, and step (e) comprises using magnetic fieldsto facilitate self-assembly onto the metal features.
 11. A methodaccording to claim 1, wherein step (e) comprises facilitatingself-assembly of the nano-sized particles onto the metal features.
 12. Amethod according to claim 1, wherein nano-sized particles comprisechaperonin, and step (e) comprises using a monolayer of alkanethiols tofacilitate self-assembly of the nano-sized particles onto the metalfeatures.
 13. A method of fabricating a patterned device, comprising:(a) providing a substrate with e-beam resist; (b) exposing anddeveloping the e-beam resist on the substrate; (c) depositing a noblemetal on the developed e-beam resist and substrate; (d) removing thee-beam resist and noble metal on the e-beam resist from the substratesuch that noble metal features remain on the substrate; (e) attachingmolecules to the noble metal features; (f) using the molecules as a maskto protect selected portions of the substrate while exposed portions ofthe substrate are etched; and (g) removing the molecules and the noblemetal features from the etched substrate to form a topographicallypatterned substrate.
 14. A method according to claim 13, wherein step(b) comprises forming holes in the resist, and step (c) comprisesdirectionally evaporating the noble metal on the developed e-beam resistand substrate to form a coating thereon.
 15. A method according to claim13, wherein step (d) comprises a lift off metallization process to stripthe e-beam resist and noble metal on the e-beam resist from thesubstrate such that noble metal features remain on the substrate.
 16. Amethod according to claim 13, wherein the molecules are proteinmolecules having a uniform size distribution that assemble into alattice structure above the noble metal features in step (e), such thatthe protein molecules reduce size and position errors in the patternedmedia.
 17. A method according to claim 13, wherein step (e) comprisesattaching a chaperonin molecule to each of the noble metal features, andstep (f) comprises reactive ion etching (RIE) the substrate.
 18. Amethod according to claim 13, further comprising removing the moleculesand the noble metal features from the substrate to form thetopographically patterned substrate.
 19. A method according to claim 13,wherein step (e) further comprises agitating the molecules to facilitateself-assembly onto the noble metal features.
 20. A method according toclaim 13, wherein step (e) further comprises bonding the molecules tothe noble metal features.
 21. A method according to claim 13, whereinthe molecules are magnetic biological agents, and step (e) comprisesusing magnetic fields to facilitate self-assembly onto the noble metalfeatures.
 22. A method according to claim 13, wherein the moleculescomprise chaperonin, and step (e) comprises using a monolayer ofalkanethiols to facilitate self-assembly of the molecules onto the noblemetal features.